Running custom docker image with cloud-on-k8s operator

I'm trying to use the cloud-on-k8s operator to deploy ES on k8s. However, I need to use a different docker image as I need to use Ubuntu instead of CentOS for compatibility with some of our packages and I also need to use debian packaged ES to be compatible with our current plugin deployment workflow.
I was able to create an ES docker image that satisfies both of the above criteria (runs Ubuntu and uses deb packaged ES), however I had some questions:

  1. The operator requires the Elastic license file to be present in /usr/share/elasticsearch (https://github.com/elastic/cloud-on-k8s/blob/1.0-beta/pkg/controller/elasticsearch/initcontainer/prepare_fs_script.go#L61), however the license file is not present in the debian distribution of ES. Is it alright if I add the license to the directory ourselves ? Is it fine to use the debian distribution with the Elastic operator (even if unsupported) ?

  2. I am using the docker-entrypoint file (https://github.com/elastic/dockerfiles/blob/7.5/elasticsearch/bin/docker-entrypoint.sh) in my Dockerfile as well, without any modifications. Am I allowed to do this ?

3.I'm also curious as to why Elastic decided to cover even Dockerfiles under Elastic license. This adds a lot of complications for us (in addition to the operator under Elastic license complicating things) even though we are just using it for internal purposes only.